1. Field of the Invention
The present invention relates to a recording apparatus including an inkjet type recording head.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2006-44021 discloses a method for preventing nozzles from drying by supplying humidified gas (hereinafter referred to as humidified gas) to an area around ink nozzles in a printer in which a plurality of inkjet recording heads are arranged along a sheet conveying direction. Spaces between adjacent recording heads are filled with supporting members and the recording heads and the supporting members are arranged to form the same flat surface, so that a continuous narrow gap area is formed. By flowing humidified gas into the gap area, the recording heads are moisturized and prevented from drying.
Although not disclosed in Japanese Patent Laid-Open No. 2006-44021, a method is known in which an image reading unit reads and analyzes an image formed by a recording head to check the state of the recording head.
The applicant of the present invention found that when an image reading unit is added to an apparatus of Japanese Patent Laid-Open No. 2006-44021, a problem related to ink mist as described below occurs.
It is reasonable to place the image reading unit near a recording unit as much as possible on the downstream side of the recording unit because it is desirable that the image reading unit reads an image immediately after the image is formed by the recording head. The apparatus of Japanese Patent Laid-Open No. 2006-44021 has a configuration in which the humidified gas flows from upstream to downstream immediately below the recording head, and then naturally diffuses in the apparatus. While recording, a large amount of ink mist is generated accompanying the ink ejected from the recording head, and the ink mist flows from upstream to downstream along with the humidified gas. Therefore, if the image reading unit is placed in an area to which the gas flows, the ink mist easily attaches to an optical system of the image reading unit, so that dirt accumulates as the operation period of the apparatus increases. When a large amount of ink mist attaches to an illumination optical system, the intensity of the illumination decreases, and when a large amount of ink mist attaches to a light receiving optical system, the intensity of the receiving light decreases. In either case, a normal quantity of receiving light cannot be obtained, and the longer the accumulated operation time of the apparatus is, the more difficult to perform a correct check is. In other words, user maintenance such as a cleaning operation of the image reading unit that is soiled with the ink mist and a component replacement operation is required to be performed frequently.
The present invention firstly provides a recording apparatus in which an image reading unit is placed on the downstream side of a recording unit, image reading can be correctly performed for a long time, and the frequency of maintenance operations by a user can be reduced.
By the way, in the apparatus of Japanese Patent Laid-Open No. 2006-44021, a means for holding and conveying a sheet is a suction belt or a suction roller, which attracts and holds a reverse surface of a sheet by an electrostatic attraction method or a vacuum suction method. However, the sheet is held only at the reverse surface, and thus the sheet may not be properly attracted due to the type or characteristics of the sheet to be used. In particular, in the apparatus of Japanese Patent Laid-Open No. 2006-44021, the humidified gas of high humidity is introduced to the suction belt or the suction roller, so that electric charge is discharged from the attraction surface due to the humidity and the holding force of the sheet significantly decreases. Therefore, a sheet having high rigidity and strong curl cannot be held only by the attraction of the reverse surface of the sheet, and the sheet floats. The quality of the recorded image degrades in a portion where the sheet floats, and there is a risk that the sheet touches the recording head when the amount of float is large. When the vacuum suction method is employed to hold the sheet in the apparatus of Japanese Patent Laid-Open No. 2006-44021, the introduced humidified gas is sucked in by the vacuum, so that the humidification efficiency deteriorates significantly.
The present invention secondarily provides a recording apparatus which, when humidified gas is introduced between the recording head and the sheet to prevent the ink nozzles from drying, any type and any sort of sheet can be reliably held and the humidified gas can be efficiently used.